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PEERING INTO THE PROTOSTELLAR SHOCK L1157-b1

PEERING INTO THE PROTOSTELLAR SHOCK L1157-b1 . C. Codella (OAA, Firenze, Italy ) on behalf of the CHESS team . M. Benedettini , A. Lorenzani , B. Nisini , M. Vasta ( Italy ) S. Cabrit, E . Caux, C. Ceccarelli , P. Hily-Blant , B. Lefloch ,

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PEERING INTO THE PROTOSTELLAR SHOCK L1157-b1

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  1. PEERING INTO THE PROTOSTELLAR SHOCK L1157-b1 C. Codella (OAA, Firenze, Italy) on behalf of the CHESS team M. Benedettini, A. Lorenzani, B. Nisini, M. Vasta (Italy) S. Cabrit, E. Caux, C. Ceccarelli,P. Hily-Blant, B. Lefloch, L. Pagani, S. Pacheco, M. Salez (France) F. Gueth, K. Schuster (IRAM), J. Cernicharo (Spain) A. Boogert, G. Melnick, D. Neufeld(USA) P. Caselli, S. Viti (UK), B. Parise (Germany)

  2. Outline The CHESS Herschel KP The L1157-B1 outflowshockregion L1157-B1: whatwelearnedfromground L1157-B1: the Herschel lesson

  3. The CHESS KP in a nutshell(PI: C. Ceccarelli, LAOG, France) ULTIMATE GOAL: chemicalsurveysduring the early phases of low-, intermediate-, and high-mass star formation; IMMEDIATE GOAL: to guide successive Herschel observations and provide a legacydatabase for the generalcommunity; METHOD: HIFI (and PACS) spectral surveys in representativeSFRs; TARGETS: fromlow- to high-massprotostars, frompre- to post-collapse, from the source to the surroundings; OUTFLOWS: to study the effects of shocks on the cloudhosting the protostar. Shocks trigger endothermicchemicalreactions, ice grain mantle sublimation or sputtering.

  4. The L1157-mm chemicalactiveoutflow Spitzer 8 μm: grey CO: contours Bachilleret al. (2001), Looneyet al. (2007), Neufeldet al. (2009) Distance: 250 pc (440 pc); Driven source: Class0protostar (IRAS20386+6751),L= 4-11 L; Mostchemicallyrichoutflowknown so far; Ideallaboratorytoobserve the effectsofshocks on the gas chemistry; Precessing molecular outflow associated with several bow shocks seen in CO and in H2.

  5. The L1157-mm chemicalactiveoutflow H2: grey CO: blue and red R2 R R0 B0 B1 B2 Severalred- and blue-bowshocksseen in CO and in H2; The brightestblue-shifted bow-shock hasbeenmappedwith the PdB and VLA arraysrevealing a rich and clumpystructure, the clumpsbeinglocated at the wallof the cavitywithanarch-shape (Tafalla & Bachiller 1995, Guethet al. 1996, 1998, Benedettini et al. 2007, Codella et al. 2009); Welltracedbymoleculesreleasedbydustmantlessuchas H2CO, CH3OH, and NH3aswellastypicaltracersofhigh-speedshockssuchasSiO.

  6. The L1157-mm chemicalactiveoutflow R2 STAR B1 R SiO(3-2) R0 B0 CH3OH(3k-2k) B1 B2 Severalred- and blue-bowshocksseen in CO and in H2; The brightestblue-shifted bow-shock hasbeenmappedwith the PdB and VLA arraysrevealing a rich and clumpystructure, the clumpsbeinglocated at the wallof the cavitywithanarch-shape (Tafalla & Bachiller 1995, Guethet al. 1996, 1998, Benedettini et al. 2007, Codella et al. 2009); Welltracedbymoleculesreleasedbydustmantlessuchas H2CO, CH3OH, and NH3aswellastypicaltracersofhigh-speedshockssuchasSiO.

  7. The L1157-mm chemicalactiveoutflow Different gas components: Slow and cold (10-20 K) swept-up material (low-J CO lines); Hot gas (2000 K) usuallytracedby H2. The link betweencold and hot components (i.e. the warmcomponent) iscrucialtounderstandhow the protostellarwindtransfersenergy back to the ambient medium. So far, temperaturesbetween 60-200 Khasbeenmeasuredusing NH3, CH3CN, and SiO (Tafalla & Bachiller 1995, Nisiniet al. 2007, Codella et al. 2009). However, a detailedstudyof the excitationconditionsof the B1 structureisstillmissing due to the limitedrangeofexcitationcoveredby the cm- and mm-observationsperformed so far. Observationsoflineswith high excitation (Eu > 50-100 K) are required.

  8. First results: the unbiased spectral survey of HIFI-Band 1b (555-636 GHz)

  9. First results: the unbiased spectral survey of HIFI-Band 1b (555-636 GHz) A total of 27 lines are identified in Band 1b, down to anaverage 3-sigma levelof 30 mK (Ta scale) . Besides CO and H2O (Leflochet al. 2010) weidentifylinesfrom NH3, H2CO, CH3OH, CS, HCN, and HCO+ (Codella et al. 2010)

  10. Origin of the Molecular Emission Bright broademission in CO and H2O up to v ≈ - 30 km/s (Vsys = +2.6 km/s) TwoVelocity Components in CO : HVC : v < -7 km/s LVC : v > -7 km/s Leflochet al. (2010) CO(6-5) @ CSO (12”) CO(6-5) averagedover 40” LVC HVC !

  11. The Low- and High-Velocity Components:fillingfactors LVC: Extended: From CO(6-5)@CSO and , SiO(2-1)@PdBI weinfer ff  1/3 HVC: Compact: SiO(2-1)/H2O intensity ratio is constant for v < -7 km/s; bothemissions arise from the sameregion : ff ≈ 0.03 SiO HVC SiO LVC Guethet al. (1998), Leflochet al. (2010), Nisiniet al. (2010)

  12. Physical Conditions in the CO Gas Derivedfrom LVG analysis of CO 5-4 usingcomplementary CO 3-2, 6-5 line (CSO observations), and assuming ff= 0.03 (HVC) and 0.3 (LVC). Leflochet al. (2010) LVC T < 100 K n(H2)= (1-3)x105 cm-3 N(CO)= 8x1016 cm-2 HVC T= > 300 K n(H2)= (1-3) x 104 cm-3 N(CO)= 5x1016 cm-2 Consistent with: LVC: warm, dense gas; HVC: warmer, less dense gas

  13. Water Emission in L1157-B1 LVG analysis (slabgeometry) of each component assuming the samephysical conditions (T, n, ff) as for CO. Ifwe assume OPR=3, T(LVC)=100 K, and T(HVC)=400 K (from CO): LVC: X(H2O) < 10-6 HVC: X(H2O) < 10-4 Higher H2O abundance in the HVC: high-Treactionsfavored and more efficient removalfrom grain mantles. In this model, the bulk of the PACS-WISH 179 µm line arises from the (unresolved) HVC Leflochet al. (2010) Preliminaryanalysis in agreement withsteady-stateC-shockmodels for HVC: Vshock 15-20 km/s in pre-shockgas n(H2)= 5 x 104 cm-3 (Gusdorf et al. 2008)

  14. Differenttracers at differentvelocities Codella et al. (2010) All the spectra (but CO and H2O) show blue-shiftedwingspeakingnear0 km/s, and with a terminal velocityequalto -8,-6 km/s. Lackof HV possibly due toS/N (PdBIspectra: HV emissionweakerthan the peakemissionby a factor 5-10). HV emissionis more diluted: HIFI data at higherfrequencieswillbeinstructive.

  15. Differenttracers at differentvelocities A secondarypeakoccursbetween -3.0 and -4.0 km/s (heredefined medium velocity, MV) and welloutlinedby e.g. HCN(7-6). The MV peakisvisiblealso in NH3 and in some linesof CH3OH and H2CO. PdBI spectra show that the MV secondary peak is observed in a couple of lines of CH3OH at 3mm and only towards the western B1b clump. Thisfindingsuggests the existenceof a velocitycomponentmainlycomingfrom the western side of B1, while the HV gas isemittedfrom the easternone.

  16. Differenttracers at differentvelocities NH3/H2O vs. Velocity: Itcouldreflectdifferent pre-shockice compositions in the MV gas. Alternatively, this behavior isconsistentwith the speculationthat NH3isreleasedbygrainmantles, whereas water isreleasedbygrainmantles and, in addition, copiouslyformed in the warmshocked gas by endothermicreactions, whichconvertallgaseousatomicoxygeninto water. Codella et al. (2010)

  17. Gas-grain shock model (Viti et al. 2004; Jiménez-Serra et al. 2008) H2O NH3 H2CO CH3OH Log(age/yr) Viti et al. (2010) - Gas grain chemical model + C-shock model + pre-existing clump at 105 cm-3; - Clear difference in the trend of the water abundance w.r.t to other species; - All species are enhanced by mantle sputtering; - During the shock period water and, to a lesser extent, ammonia are also enhanced but water is the only species that is maintained high even after the shock has passed.

  18. Different gas components…. In agreement with the old 30-m results Codella et al. (2010) Twocomponents at differenttemperatures or non-LTEeffects and lineopacity? The presentobservationsprovide a link between the gas at Tkin 60--200 K (NH3, CH3CN, SiO) previouslyobservedfromground and the warmer gas probedby the H2lines.

  19. Different gas components…. In agreement with the old 30-m results Codella et al. (2010) Floweret al. (2010) Twocomponents at differenttemperatures or non-LTEeffects and lineopacity? The presentobservationsprovide a link between the gas at Tkin 60--200 K (NH3, CH3CN, SiO) previouslyobservedfromground and the warmer gas probedby the H2lines.

  20. L1157-mm H2 S(1) 17 m Different gas components…. B1 position dN  T- Nisiniet al. (2010) Fitof H2mid- and NIR-datausing a temperature stratificationmodel (from 300 to 4000 K)

  21. Whataboutotheroutflows? In agreement with the old 30-m results RED Trot = 14 K BLUE Trot = 13 K NGC1333-IRAS 2 (Bachilleret al. (1998)

  22. Physicalpropertiesalong the B1 bow shock Codella et al. (2010) LVG: CS(12-11), HIFI, and CS(2-1), (3--2), PdBI: we derive a kinetic temperature definitelyabove 300 K. Caution: wecould trace different gas components, assuggestedbymethanol, the gas at higherexcitation beingtracedby CS(12-11). Densitiesaround 104 cm-3. LV gas denserthan the MV one?

  23. PACS-CHESS spectral survey (55-210m) of L1157-B1 OI 63 m o-H2O CO(14-13) o-H2O p-H2O CO(15-14) o-H2O o-H218O • Preliminary PACS results: • AT LEAST: CO lines: fromJ = 14-13 to 22-21 • 7 H2O lines, OI @ 63 m, OH @ 119 m • Excitation vs. position & FillingFactor PACS In addition: other HIFI-CHESS spectraso farobserved: CO: from 6-5 to 10-9, 14-13, 16-15 + 13CO: 8-7 H2O: 111-000, 312-303, 312-221, 212-101, 221-212 HCl: 1-0 + C+ @ 157 μm

  24. PEERING INTO A PROTOSTELLAR SHOCK: CONCLUSIONS The molecularemission arises from 2 physically distinct regions: LVC : warm, extended, chemicallyrich dense gas, withinternal structure revealedfromspecifictracers : high-velocities from the eastern side, high-densities on the western side. HVC : hot, compact, lowerdensitygas. Less densemedium towardsB1b(MV peak)? H2O abundanceincreases by 2 orders of magnitude between LVC and HVC. SiO HVC SiO LVC 55 K 92 K 67 K 73 K 132 K Codella et al. (2009, 2010)

  25. Origin of the Molecular Emission Leflochet al. (2010)

  26. The L1157-mm chemicalactiveoutflow Bachilleret al. (2001)

  27. PACS-WISH KP mapof179 µmline in L1157 H2 17µmNeufeldet al. (2009), H2O 179 µmNisiniet al. (2010) SiO(2-1) @ PdBIGuethet al. (1998) CO(2-1), SiO(3-2) Bachilleretal. (2001) H2O localized on the CO peaksof the precessing jet Correlationbetween H2O and H2warm gas at T ~ 300 K H2O followsSiO--> tracerof high density shockswithV > ~ 20 km/s

  28. PACS mapof179 µmline in L1157 Herschel PACS Spitzer IRAC H2O 179 m H2: grey CO: blue and red PACS observations: 9.4”/pixel, 6’x2’ rastermap R(179 µm) ~ 1500 L1157 mm 104 AU Strong water emissionfrom the embeddedprotostar Emissionpeaks trace the shock interactionregions

  29. The Low-Velocity Component Extended: From CO(6-5)@CSO and , SiO(2-1)@PdBI weinfer ff  1/3 SiO HVC SiO LVC Guethet al. (1998), Leflochet al. (2010)

  30. The High-Velocity Component SiO HVC SiO LVC Guethet al. (1996, 1998), Leflochet al. (2010) • SiO(2-1)/H2O intensity ratio is constant for v < -7 km/s • Bothemissions arise from the sameregion : ff ≈ 0.03 (4” x 12”, PdBI) • Emission isopticallythick

  31. Water Emission in L1157-B1 LVG analysis (slabgeometry) of each component assuming the samephysical conditions (T, n, ff) as for CO and takingintoaccount the total 179 µm line flux (PACS-WISH, Nisini et al. 2010). Leflochet al. (2010) • Ifwe assume OPR=3, T(LVC)=100 K, and T(HVC)=400 K (from CO): • LVC: N(H2O)= (4.0-5.0) x 1014 cm-2 X= (0.7-0.8) x 10-6 • HVC: N(H2O)= (2.5-3.0) x 1016 cm-2 X= (0.6-0.8) x 10-4 • Higher H2O abundance in the HVC: high-Treactionsfavored and more efficient removalfrom grain mantles. • In this model, the bulk of the 179 µm line arises from the (unresolved) HVC

  32. Water Emission in L1157-B1 LVG analysis (slabgeometry) of each component assuming the samephysical conditions (T, n, ff) as for CO and takingintoaccount the total 179 µm line flux (PACS-WISH, Nisini et al. 2010). Preliminaryanalysis in agreement withsteady-stateC-shockmodels for HVC: Vshock 15-20 km/s in pre-shockgas n(H2)= 5 x 104 cm-3 (Gusdorf et al. 2008) Leflochet al. (2010) • Ifwe assume OPR=3, T(LVC)=100 K, and T(HVC)=400 K (from CO): • LVC: N(H2O)= (4.0-5.0) x 1014 cm-2 X= (0.7-0.8) x 10-6 • HVC: N(H2O)= (2.5-3.0) x 1016 cm-2 X= (0.6-0.8) x 10-4 • Higher H2O abundance in the HVC: high-Treactionsfavored and more efficient removalfrom grain mantles. • In this model, the bulk of the 179 µm line arises from the (unresolved) HVC

  33. Gas-grain shock model (Viti et al. 2004; Jiménez-Serra et al. 2008) N(H2) H2O NH3 Tkin H2CO CH3OH Log(age/yr) Viti et al. (2010) - Gas grain chemical model + C-shock model + pre-existing clump at 105 cm-3; - Clear difference in the trend of the water abundance w.r.t to other species; - All species are enhanced by mantle sputtering; - During the shock period water and, to a lesser extent, ammonia are also enhanced but water is the only species that is maintained high even after the shock has passed.

  34. Forthcoming analysis:PACS-CHESS spectral survey (55-210m) of L1157-B1 OI 63 m o-H2O CO(14-13) o-H2O CO(15-14) p-H2O o-H2O o-H218O PACS • Preliminaryresults: • AT LEAST: CO lines: fromJ = 14-13 to 22-21 • 7 H2O lines, OI @ 63 m, OH @ 119 m • Excitation vs. position • Fillingfactors

  35. PACS-CHESS spectral survey (55-210m) of L1157-B1 OI 63 m o-H2O Other HIFI-CHESS spectraso farobserved: CO: from 6-5 to 10-9, 14-13, 16-15 13CO: 8-7 H2O: 111-000, 312-303, 312-221, 212-101, 221-212 HCl: 1-0 C+ @ 157 μm CO(14-13) o-H2O p-H2O CO(15-14) o-H2O o-H218O PACS • Preliminaryresults: • AT LEAST: CO lines: fromJ = 14-13 to 22-21 • 7 H2O lines, OI @ 63 m, OH @ 119 m • Excitation vs. position • Fillingfactor

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